Hydraulic system for a slide

ABSTRACT

The invention relates to a form tool for injection-molding molded articles ( 6 ), especially PET parisons. The form tool comprises a base plate ( 2 ) and a stripper plate ( 3 ) having a slide ( 4 ). A plurality of separable male mold cones ( 5, 5′ ) is provided on the slide ( 4 ). For removing the parisons ( 6 ), the male mold cones ( 5, 5′ ) are completely opened using a hydraulic drive ( 12 ) instead of an inclined drag element.

The present invention relates to a multipart male mold plate for a formtool for injection-molding of molded articles according to the preambleof claim 1.

Such male mold plates are used in injection-molding form tools asdisclosed for example in EP 0 647 514 and comprise a base plate and astripper plate having a slide, wherein the slide supports a plurality ofseparate male mold cones. In opening such form tool the multipart malemold plate is retracted in order to expose or uncover the freshlyinjected molded blanks, in particular preforms, i.e. to pull them fromthe female mold or die. There is provided a removal device between thedie and the male mold plates to extract the preforms, for example asdescribed in EP 0 907 488. To remove the preforms, the stripper plate,which is provided with a slide, is separated from the base plate and theslide is guided along an inclined drag element. By this means thevarious male mold cones are opened and the preforms can be transferredto the removal device. For this, pressurised air is used, by means ofwhich the preforms are ejected from the opened male mold cones. Thelength of the preforms, generally 8 to 12 cm, permits insertion of thepreforms in the removal device before the various male mold cones arecompletely open. This ensures a secure transfer of the preforms from themale mold cones to the removal device.

However in removing particularly short preforms, i.e. preforms with alength of about 3 to 5 cm, the secure intake or capture of the preformsin the respective removal sleeves of the removal device is not ensured,because the removal sleeves of the removal device cannot be broughtclose enough to the external extremity of the preforms, or because theseparable male mold cone has a relatively long opening distance, forexample about 5 cm or more.

It is therefore an object of the present invention to provide a deviceby means of which relatively short preforms can be removed in a securemanner.

This object is achieved according to the invention by means of a malemold plate having the features of claim 1, and in particular by means ofa male mold plate whose slide is actuatable by means of a hydraulicdrive.

With the male mold plate according to the invention, the freshlyinjected preforms are retained or held back until they reach a removalsleeve of the removal device and are safely guided therein. Only thenare the male mold cones completely opened according to the inventionwith the aid of a hydraulic drive, instead of with an inclined dragelement, and the preforms can be securely sucked into the removalsleeves. Obviously, the opening of the male mold cones is started asearly as possible in order to keep the cycle time of the tool as shortas possible.

The advantages of such a male mold plate are immediately apparent to theperson skilled in the art and are to be seen in particular in theshortening of the opening distance necessary for opening the male moldcone. Other advantages are to be seen in that pressurised air previouslyused is no longer required for removing the preforms and, as aconsequence, the contamination of the preforms caused by thispressurised air can be avoided.

Other advantageous embodiments of the present invention are disclosed bythe features of the dependent claims.

In a first preferred embodiment the hydraulic drive is attached orsecured to the slide and rests against the stripper plate. Obviously thehydraulic drive can be secured also to the stripper plate and the slidecan be actuated from there.

In a preferred embodiment the hydraulic drive serves to completely openthe male mold cones and there is provided a pull-back spring to againclose the open male mold cones. Naturally the expert can open the malemold cones by means of a spring force and can close them by means of thehydraulic drive. Advantageously the inclined drag element is providedwith a step or swell at a location between a separation position and anextraction position, which displaces the slide by a detachment stroke.By means of this detachment stroke of less than 1 mm the preform issimply detached from the respective male mold cone, to avoid that thepreform remains stuck to one half of the male mold cones when these areopened.

In the following the invention is described in more detail by means ofan exemplary embodiment and with the help of the Figures which show:

FIG. 1 a male mold plate of the known art in the extraction position,

FIG. 2 a male mold plate according to the invention in the extractionposition.

FIG. 1 shows a multipart male mold plate 1 of a known type, whichincorporates a base plate 2, a stripper plate 3 and a slide 4. Thisslide 4 bears several separable male mold cones 5, 5′. When opening theform tool the complete male mold plate is retracted for extracting thepreforms 6 from the die (not shown) In a further cycle stage thestripper plate 3 is brought from a separation position A into anextraction position B. Thereby the slide 4 moves along an inclined dragelement 7 which is securely attached to the base plate 2, which dragelement 7 defines an opening distance s. This completely opens the malemold cones 5. The completely opened male mold cones are indicated byreference numeral 5′. FIG. 1 shows clearly that in opening the male moldcones 5, the individual preforms 6 are no longer securely held and inthe extraction position B of the male mold cones 5′ the preforms cancant and therefore can no longer be extracted. To effect the extractionof the preforms 6, pressurised air 11 is introduced into the open malemold cone 5′ of this tool of the known art. This pressurised airgenerally carries dirt or oil particles and contaminates the freshlyinjected preforms. In addition, FIG. 1 shows clearly that the male moldcones 5′ in the extraction position B and the removal device 8,respectively its removal plate 9 and removal sleeve 10, cannot bebrought closer to each other, since in the case of a successfulextraction of the preform, the latter would again be caught up by theclosing male mold cone 5′ during the retraction of the stripper plate 3and would thus be pulled out from the removal sleeve 10.

FIG. 2 shows an arrangement of the male mold plate 1 according to theinvention, again with separable male mold cones 5 in their separationposition A, as well as an opened male mold cone 5 in the extractionposition B. The base plate 2 has a laterally arranged inclined dragelement 7 which has only at position C a step or swell to cause adetachment stroke h. By means of this detachment stroke h the preformsare merely loosened or detached from the male mold cones to ensure thatthe preforms, during the complete opening of the male mold cones 5, donot remain stuck to the latter. The slide 4 is movably attached to thestripper plate 3, which slide supports the separable male mold cones 5.In the zone of the extraction position B the male mold cone 5 is openedby means of a hydraulic drive 12. In this embodiment the hydraulic drive12 is secured to the slide 4 and rests against the stripper plate 3.

FIG. 2 shows clearly that the opening distance s can be shortenedsignificantly by using a hydraulic drive and thus the preforms 6 can bebrought into the extraction sleeves 10 of the extraction device 8,before the male mold cones 5 are completely open. Furthermore, thisshortened opening distance allows to bring the extraction plate 9 of theextraction device 8, and the extraction sleeve 10, closer to thecompletely open male mold cones 5′ by a distance d. This ensures asecure removal of extremely short preforms. Moreover it is possible todispense with the use of pressurised air for the transfer of preforms,thereby avoiding the associated contamination. Advantageously in asubsequent cycle stage, the male mold cones 5′ are again brought into aclosing position by means of a pull-back spring engaged at the slide 4.

1. Multipart male mold plate (1) for a form tool for injection-molding of molded articles, in particular pet preforms (6), said male mold plate (1) comprising a base plate (2) and a stripper plate (3) having a slide (4), on which slide (4) there is provided a plurality of separable male mold cones (5, 5′), and there is provided at least one hydraulic drive (12) for completely opening the male mold cones (5, 5′), characterized in that the hydraulic drive (12) is secured to the slide (4) and rests against the stripper plate (3).
 2. Male mold plate according to claim 1, characterised in that the hydraulic drive (12) cooperates with a pull-back spring.
 3. (canceled)
 4. Male mold plate according to claim 1, characterised in that the hydraulic drive (12) cooperates with a second hydraulic drive for opening the male mold cones (5, 5′).
 5. Male mold plate according to claim 1, characterised in that an inclined drag element (7) is secured to the base plate (2) and actuates the slide (4) in such a way that it opens the male mold cones (5, 5′) merely for a detachment stroke (h) at a position (C) between a closing position (A) and an extraction position (B). 